Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$177.69	8.229%	$192.3121	$192.31	$192.30	$192.30
Purchase #2	$91.81	8.865%	$99.949	$99.95	$99.95	$99.90
Purchase #3	$90.80	10.530%	$100.3612	$100.36	$100.35	$100.40
Purchase #4	$52.63	5.473%	$55.5104	$55.51	$55.50	$55.50
Purchase #5	$182.88	7.317%	$196.2613	$196.26	$196.25	$196.30
Purchase #6	$92.58	11.181%	$102.9314	$102.93	$102.95	$102.90
Purchase #7	$198.31	10.484%	$219.1008	$219.10	$219.10	$219.10
7 purchase totals =	$886.70		$966.4262	$966.42	$966.40	$966.40